Comment regarding the "up" value for the rel attribute

Hi,

I would like to suggest an improvement to a very specific part of HTML
5; the up type for the rel attribute
(http://dev.w3.org/html5/spec/Overview.html#link-type-up). It is a
really helpful this addition but I think it could be optimized. The
repitition of the up value to specify the depth of the relationship
makes it harder to parse (especially for XSLT where string parsing is
limitted). Perhaps specifying one up followed by a delimiter and a
number specifying the depth (example: up;1, up:2, up:3).

Thoughts?